h264 profiles

[rxnelson]

I was looking at the h264 built in profiles in 4.9 and it made me curious. I saw that the HD (High) does indeed have a very high bitrate (6835) but is relatively low res(720x480). Isn't part of what makes HD look great the high resolution? I didn't think you could overcome that with high bitrate. Anyway, just curious if anyone uses that or if they bumped up the resolution.

[obperryo]

Originally Posted by rxnelson

I was looking at the h264 built in profiles in 4.9 and it made me curious. I saw that the HD (High) does indeed have a very high bitrate (6835) but is relatively low res(720x480). Isn't part of what makes HD look great the high resolution? I didn't think you could overcome that with high bitrate. Anyway, just curious if anyone uses that or if they bumped up the resolution.

Here is what I have figured out in all my testing on squeezing.

Bitrate is the amount of data avaliable to build the picture, and determines file size.

Resolution is just identifying what size the video should be when initiated.
What I mean by this is that is the size frame VLC or WMP will open up to when you launch the video. If you are on a bigger monitor and you have a high bit rate, can make the window bigger and still have a good picture.

To optomize squeezing a video you first decide what window size you need and then lower the bit rate to the value needed for a good picture, and this makes the smallest file possible for a good picture. So, here by design, you will beging to see the quality of the picture drop as soon as you start to increase the window size.

Now, use a smaller resolution with identified bitrate. Note, the greater the resolution, the great the CPU (if not hardware accelerated) needed to write to the screen. With the bitrate of a larger resolution used with a smaller resolution, you require less CPU, but still have enough data so you can stretch the picture to match the larger resolution. So, use a bitrate for a larger resolution, but squeeze the video to a smaller resolution.

Now, as I figured all this out for DIVX, I encountered a problem when it came to h264. Setting the resolution smaller and stretching it, caused edges to be jagged. The further you are from your TV resolution, the greater the jagged edges. I still have not figured out how to clean this up like DIVX does, but for now, I can take a 1920x1080i to 1024x576p and stretch it to 1366x768 and the jagged edges are not bad at all and my small CPU can play it.

Also, note, the greater the motion in the video and the smaller the objects (football), the greater the bitrate is needed. And, the less the video moves, the less the bitrate needed.

There are a lot of bitrate calculators out there but they are all designed to make a video fit to a size disc. I have not found one that gives you picture quality rating based on bitrate, except this one...
http://www.adobe.com/devnet/flash/ap...te_calculator/
and I am asuming that based on it being Adobe and them giving bitrates for slow, avg and fast video that these are rates for quality video.

With all of this, you have to decide what level of quality is right for you.